The present invention relates to a digital map data processor and a digital map data processing method, and more particularly to a processor and processing method for digital map data generated from ground surface photographic data.
Navigation systems, which by use of Global Positioning System (GPS) satellite signals are able indicate the position of the vehicle on which they are installed and to provide a route for guidance to a destination are recently becoming increasingly common. There has also been proposed a dynamic route guidance system (DRGS) which uses a VICS (Vehicle Information Communication System) to obtain traffic information such as link traveling time from an information center, retrieves a traveling route recommended for reaching a destination in the shortest time according to the obtained traffic information, and provides this route to the user (driver or the like). A user of such a system recognizes the traveling route and various information provided by the system as shown on a display or guided by voice. With the route guiding information, the user is able to operate the vehicle to drive more comfortably and without tiring so much.
A navigation function used by the aforesaid system may comprise a dead-reckoning navigation, map matching, GPS, and the like. In dead-reckoning navigation, a running track of a vehicle is determined from a relative position of a vehicle as determined using direction and distance sensors mounted on the vehicle. In map matching, the running track of the vehicle is determined by dead-reckoning navigation with the road form on the map data to judge the traveled road, thereby determining a position of the vehicle on a map. The position accuracy of map matching can be improved by joining with an absolute position (latitude and longitude) information of the vehicle obtained by the GPS.
For the user to recognize the information provided by the aforesaid system without feeling a sense of incongruity, the actual state around the vehicle (road forms and surrounding buildings) should agree with the displayed contents which are displayed together with the pertinent vehicle on the display device or the like. Therefore, a map accurately indicating the position of the pertinent vehicle is required.
It is desirable to use map data which is corrected by performing actual measurement, building investigation, and the like, but problems related to the enormous map making time and cost, very long update intervals(e.g., every year), and less than optimum timing remain obstacles.
Japanese Patent Application Laid-Open Publication No. Hei 7-28400 discloses a technology wherein satellite image data captured by an earth observation satellite is transmitted to vehicles and the like on the ground, the satellite image is converted into a map background image, and the background image is combined with previously generated place name data and road data to generate the map. According to this technology, satellite image data of the ground surface photographed at a relatively short cycle can be obtained, so that the map can be updated relatively frequently. The position of the vehicle is displayed on the background image which is an actual photo image and the user can readily see the buildings and surrounding environments (a surrounding image of the vehicle) on the map. Thus, the degree of recognition of information is improved.
With the above method, however, the obtained photo of the ground surface is only an image and does not include data related to place names and the like linked to roads and a distance of each link of the roads to calculate the route. Therefore, there is a disadvantage that conventional navigation functions for sophisticated route calculation (e.g., toll road priority retrieval, cost priority retrieval, etc.), route guidance (avoidance of a traffic jam, avoidance of traffic restriction, etc.), warning control (warning of a curve, warning of an uphill or downhill slope, etc.), and the like cannot be made. Also, because photographs are taken from different photographing angles with photographing timing, the photographed road forms and the like differ from actual ones. As a result, when the previously generated road data, place name data and the like are overlaid, the places shown on the photo are displaced from the places (latitude and longitude) of the each data.
Therefore, there is a problem that when various types of information are composed, total map accuracy is degraded, and the calculation by the aforesaid navigation function cannot be conducted accurately. There is also a disadvantage that the position shown on the photo is displaced from the position of the pertinent vehicle recognized by the GPS, and the navigation itself becomes meaningless.
The present invention was achieved to remedy the aforesaid problems and it is an object of the invention to provide a digital map data processing device and a digital map data processing method which can obtain accurate road map data by using data which can be obtained easily and frequently and use the obtained data effectively.
The present invention is directed to a digital map data processing device which comprises image data acquiring means which obtain image data of the ground surface captured from a high point of view; image processing means which convert the image data into orthoimage data viewed substantially from directly above; data extraction means which extract road network data of the ground surface on the basis of the orthoimage data; data conversion means which convert the road network data into a data format corresponding to a predetermined digital road map; and map generating means which generate digital orthomap data by overlaying the converted road network data on the predetermined digital road map.
The image data of the ground surface photographed from a high point of view may be image data captured by high-altitude aircraft such as an airplane or a satellite. Here, orthoimage data viewed substantially from directly above does not necessarily mean a complete vertical to the ground surface, but to the extent that the roads and buildings on the ground surface are viewed plane. Also, the road network data includes roads and three-dimensional information (e.g., terrain, facility appearance, etc.) related to the roads, and the data conversion means add altitude information and the like related to roads and a distance of each link and the link division to the roads of the extracted road network data. In addition, the map generating means overlay place name information, name information, road-related control information and the like on the network data to generate the road map. By configuring in this way, the road network data extracted from the image data in an orthogonally projected state and viewed substantially from directly above has roads in accurate forms corresponding to actual latitude and longitude, so that when various types of information are overlaid, the information is free from displacement, and a map of high accuracy can be generated. The road network is extracted on the basis of the orthoimage data having all the areas viewed from directly above. Therefore, accurate map data corresponding to the actual roads can be obtained.
In the aforesaid structure, the present invention may include a feature that the data extraction means include comparison means which compare first orthoimage data converted at a first time with second orthoimage data converted at a second time to obtain change portion data between them, and the map generating means correct the digital orthomap data according to the change portion data.
With the above configuration, map data may be corrected for only portions changed between the first time and the second time. Therefore, the map generating cost can be reduced, and the map data can be updated frequently.
In the aforesaid structure, the present invention may further comprise transfer means which transfer the generated digital orthomap data to an external map data processing system.
The external map data processing system may be a navigation system using the map data to perform various types of processing and various retrieval systems, which are used at any place such as a vehicle and an information center. The transfer means may also include storage means, such as CD-ROM and DVD, in addition to wired or wireless communication means to transfer. By configuring as described above, the highly accurate map data can be used with ease.
With the aforesaid structure, the present invention may have a feature that image data acquired by the image data acquiring means is satellite image data captured by an artificial satellite.
By configuring as above, the image data can be obtained frequently, and the latest road data can be obtained. Therefore, the map data can be updated easily and accurately with desired timing.
The present invention is also directed to a digital map data processing method, which comprises an image data acquiring step which obtains image data of the ground surface captured from a high point of view; an image processing step which converts the image data into orthoimage data viewed substantially from directly above; a data traction step which extracts road network data of the ground surface on the basis of the orthoimage data; a data conversion step which converts the road network data into a data format corresponding to a predetermined digital road map; and a map generating step which generates digital orthomap data by overlaying the converted road network data on the predetermined digital road map.
The present invention is also directed to a medium on which generation software for generating digital orthomap data is recorded, characterized in that the generation software is executed on a computer and includes: a module which processes to convert image data of the ground surface captured from a high point of view into the orthoimage data viewed substantially from directly above, a module which extracts road network data of the ground surface according to the orthoimage data, a data conversion module which converts the road network data into a data format corresponding to a predetermined digital road map, and a module which generates digital orthomap data by overlaying the converted road network data on the predetermined digital road map.
The present invention is also directed to a digital map data processing device, which comprises data acquiring means which obtain digital orthomap data generated according to image data of the ground surface photographed from a high point of view; writing means which write the acquired digital orthomap data into map storage means associated with a navigation system; and control means which control the navigation system according to the written digital orthomap data.
The data acquiring means may also include the reading of data from the wired or wireless communication means or from the storage means such as CD-ROM or DVD. By configuring as above, the map generated according to the road network data extracted from the image data, which is in the orthogonally projected state and viewed substantially from directly above, has the road forms corresponded to the actual latitude and longitude and the various types of information overlaid without being displaced. Thus, the map is very precise, and the navigation can be controlled very accurately.
In the aforesaid structure, the present invention may have a feature that the control means also control a vehicle-mounted running control device.
The running control equipment may include, for example, acceleration control, shift control, brake control, suspension control, drive wheels control and steering control equipment. The digital orthomap data may include altitude data in addition to the latitude and longitude so that a road inclination and a radius of curvature of a curve can be calculated accurately. For example, shift control and acceleration control for deceleration before a curve and an uphill or downhill inclination lane can be made with appropriate timing in an appropriate amount of control. Thus, vehicle control can adjust to terrain.
The present invention is also directed to a digital map data processing method, which comprises an acquiring step which obtains digital orthomap data generated according to image data of the ground surface photographed from a high point of view; a writing step which writes the acquired digital orthomap data into map storage means associated with a navigation system; and a control step which controls the navigation system according to the written digital orthomap data.
In the aforesaid structure, the present invention may have a feature that the control step also controls a vehicle-mounted running control device.